1. Field of the Invention
The present invention relates to a technique for implementing data communication and distance measurement in a wireless communication apparatus.
2. Description of the Related Art
Ultra-wide band (UWB) has become the focus of attention in recent years. The radio signal used in UWB has a bandwidth of 500 MHz or greater, or a bandwidth that is 20% of the center frequency or greater. This makes possible the communication of large quantities of data at high speed.
It is also known that UWB makes it easy to implement a highly precise distance measurement function. The specification of Japanese Patent Application Laid-Open No. 2003-174368 discloses a method of finding the distance to an obstacle by measuring the time from transmission of a UWB pulse to return of the pulse reflected by the obstacle.
Further, the specification of Japanese Patent Application Laid-Open No. 2005-065072 proposes a method of measuring distance in UWB that employs an OFDM (Orthogonal Frequency Division Modulation) scheme.
The standardization of wireless USB has been proceeding in recent years. There is a high likelihood that wireless USB also will employ the above-mentioned UWB scheme in the physical layer. At present it appears that data communication with wireless USB will be performed using the MAS (Media Access Slot) that constructs a superframe. A beacon is inserted into a superframe every 65 ms.
In wireless USB, however, a concrete method for measuring distance has not been proposed.